Methods and apparatus for electrostatic chuck repair and refurbishment

ABSTRACT

In one embodiment of the invention, a substrate support assembly comprises an electrostatic chuck having an electrode embedded therein and having an aperture disposed therethrough, a conductive liner disposed on the surface of the electrostatic chuck within the aperture, a conductive tubing extending from a lower surface of the electrostatic chuck and axially aligned with the aperture, and a conductive coating at least partially within the aperture and at least partially within the conductive tubing, wherein the conductive coating provides a conductive path between the conductive liner and the conductive tubing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 61/792,480, filed Mar. 15, 2013, which is hereby incorporatedby reference herein.

BACKGROUND

1. Field

Embodiments of the present invention generally relate to apparatus andmethods for refurbishing an electrostatic chuck. More specifically, torepairing a severed electrical connection in the balancing circuit of anelectrostatic chuck.

2. Description of the Related Art

In substrate processing equipment, an electrostatic chuck is commonlyused for clamping a substrate to a pedestal during processing. Theelectrostatic chuck clamps the substrate by creating an attractive forcebetween the substrate and the chuck. A voltage is applied to one or moreelectrodes in the chuck to induce oppositely polarized charges in thesubstrate and the electrodes, respectively. The opposite charges pullthe substrate against the chuck, thereby retaining the substrate.

In a bipolar, electrostatic chuck, a chuck body has a pair of coplanarelectrodes embedded therein. Each electrode is respectively connected toa terminal of a dual power supply having a common terminal, which isreferred to as a center tap. The center tap is connected to a substratespacing mask provided on the surface of the chuck in order to balanceany variations in the impedance between the substrate and theelectrodes. Thus, a constant electrostatic attraction force between thesubstrate and the chuck is maintained across the surface of the chuck.

The electrical connection between the center tap and the substratespacing mask is often made through the conductive wall of a gas conduitused to supply gas to the backside of the substrate during processing.The gas conduit is attached to a metalized central bore within the chuckbody. This connection works well during substrate processing, but theconductive connection is sometimes disrupted or otherwise compromisedover time. While the conductive connection may remain mechanicallysound, the connection may not be effectual in conducting electriccurrent, which results in improper or dysfunctional operation of theelectrostatic chuck.

Conventional repair methods include re-establishing the conductiveconnection using welding techniques, such as electron beam welding orlaser welding techniques. However, these methods are expensive and timeconsuming, which increases cost of ownership and extends chamberdowntime.

Therefore, a need exists for apparatus and methods of restoring acompromised balancing circuit electrical connection in an electrostaticchuck.

SUMMARY

In one embodiment of the invention, a substrate support assemblycomprises an electrostatic chuck having an electrode embedded thereinand having an aperture disposed therethrough, a conductive linerdisposed on the surface of the electrostatic chuck within the aperture,a conductive tubing extending from a lower surface of the electrostaticchuck and axially aligned with the aperture, and a conductive coating atleast partially within the aperture and at least partially within theconductive tubing, wherein the conductive coating provides a conductivepath between the conductive liner and the conductive tubing.

In another embodiment, a method for repairing a severed electricalconnection within a balancing circuit of an electrostatic chuck assemblycomprises applying a conductive fluid across the severed electricalconnection, and curing the conductive fluid to establish a conductivepath across the severed electrical connection.

In another embodiment, a method for repairing a severed electricalconnection within a balancing circuit of an electrostatic chuck assemblycomprises determining the resistance between a substrate spacing maskdisposed on the upper surface of an electrostatic chuck and a conductivetubing extending from the lower surface of the electrostatic chuck andaxially aligned with a metallically lined aperture extending through theelectrostatic chuck, evaluating the determined resistance to determinewhether the electrical connection between the conductive conduit and thesubstrate mask has been severed, and repairing the severed connection byrestoring a conductive path between the conductive tubing and thesubstrate spacing mask by applying a coating comprising a nano-particleconductive material.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic, cross-sectional view of an exemplary substratesupport assembly, which may benefit from the present invention.

FIG. 2 is a schematic depiction of a substrate support assemblyutilizing a method of repairing a severed electrical connection betweena conductive gas conduit and a conductive passage according to oneembodiment of the present invention.

FIG. 3 is a schematic, cross-sectional view of another substrate supportassembly that may benefit from the invention.

FIG. 4 is a schematic, cross-sectional view of another substrate supportassembly that may benefit from the invention.

FIG. 5 is a schematic top plan view of a substrate support assemblyshowing the center tap structure described in FIGS. 3 and 4.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

The present invention includes methods and apparatus for testing andrepairing an electrical connection between bipolar electrodes containedwithin an electrostatic chuck and a conductive mask disposed atop theelectrostatic chuck, particularly after removal of the electrostaticchuck. This connection is known as a balancing circuit because itbalances the electrostatic forces applied to a substrate positioned atopthe electrostatic chuck.

In one embodiment, the electrostatic chuck is tested to determinewhether the balancing circuit electrical connection has been disrupted.In one embodiment, if the electrical connection has been disrupted, theelectrical connection is repaired via a conductive coating process.

FIG. 1 is a schematic, cross-sectional view of an exemplary substratesupport assembly 100, which may benefit from the present invention. Thesubstrate support assembly 100 includes an electrostatic chuck 105 forsupporting and retaining a substrate 102 during processing. Theelectrostatic chuck 105 may comprise aluminum (Al) or an aluminumcontaining ceramic material, such as Al/Al₂O₃/AlN, or other material.

The electrostatic chuck 105 has a substrate spacing mask 107 disposed onthe upper surface thereof. The substrate spacing mask 107 may comprise amaterial such as titanium, titanium nitride, or diamond-like carbon, andthe like. The substrate spacing mask 107 is deposited to a pre-definedthickness that maintains the substrate 102 slightly above the surface ofthe electrostatic chuck 105. The electrostatic chuck 105 furthercontains a conductive passage 103 disposed therethrough. In oneembodiment, the conductive passage 103 electrically couples thesubstrate spacing mask 107 to the bottom region of the electrostaticchuck 105.

In one embodiment, a heat transfer fluid is transported from a gassource 130 to a conductive gas conduit 132 through a gas conduit 135.The conductive gas conduit 132 is mechanically and electrically coupledto the conductive passage 103, such as by brazing. In one embodiment,the conductive gas conduit 132 is conductive tubing, such as stainlesssteel tubing. In one embodiment, the conductive gas conduit is axiallyaligned with the conductive passage 103. Heat transfer fluid istransported through the conductive gas conduit 132 to the passage 103extending through the electrostatic chuck 105. The gas is furthertransported through the conductive passage 103 to the backside of thesubstrate 102. The flow of gas may provide heating or cooling to thebackside of the substrate 102. The heat transfer gas may be helium,argon, hydrogen, among others.

The electrostatic chuck 105 includes one or more chucking electrodes 110embedded therein. The chucking electrodes 110 are fabricated from aconductive material, such as tungsten, graphite, copper, or the like.The chucking electrodes 110 are disposed in an upper region of theelectrostatic chuck 105 to provide the necessary electrostatic force toretain the substrate 102 when energized. The chucking electrodes 110 maybe configured in any manner necessary to electrostatically retain thesubstrate 102. However, in the embodiment depicted in FIG. 1, thechucking electrodes 110 are in a bipolar configuration.

The chucking electrodes 110 are connected to a power supply 140comprising a pair of dual terminal DC voltage supplies 162 and 164 witha center tap 166. The cathode on the voltage supply 162 is coupled toone of the bipolar chucking electrodes 110 via an electrode lead 163,and the anode from the other voltage supply 164 is coupled to the otherbipolar chucking electrode 110 via an electrode lead 165. The cathode ofthe voltage supply 164 is coupled to the anode of the voltage supply 162with a center tap 166 coupled therebetween. The center tap 166 isfurther coupled to the substrate spacing mask 107 via the conductive gasconduit 132 and the conductive passage 103. A first brazed joint 170 maybe used to electrically and mechanically couple the conductive gasconduit 132 to the conductive passage 103. A metalized layer 175 may beused to electrically and mechanically couple the substrate spacing mask107 to the conductive passage 103. The first brazed joint 170 and themetalized layer 175 may comprise a conductive metallic material, such asgold (Au), silver (Ag) or aluminum (Al) or other conductive material. Inone embodiment, the metalized layer 175 may be a tungsten (W) paste thatis sintered to form a metallic layer and electrically connect thesubstrate spacing mask 107 to the conductive passage 103. The electricalconnection between the substrate spacing mask 107 and the conductivepassage 103 comprising the metalized layer 175 can also include carbonnano tubes or graphene sheet or foils. The metalized layer 175 can alsocomprise multiple layers of the conductive metallic material, nano tube,sheets or foil as described herein, that include a corrosion resistantupper layer and a conductive inner metal contact made of nano ink orpaste. Thus, a mechanically and electrically stable connection is formedbetween the center tap 166 and the substrate spacing mask 107. As such,variations in the electrostatic force due to physical variations in thedistance between the substrate 102 and the chucking electrode 110 may bebalanced. Therefore, changes in the electrostatic force are balanced byhaving the center tap 166 of the power supply 140 coupled to thesubstrate spacing mask 107 in a balancing circuit.

Periodic service and maintenance of the substrate support assembly 100is required during the lifetime of a processing chamber housing theelectrostatic chuck 105. Accordingly, the electrostatic chuck 105 may beperiodically removed from its processing chamber for refurbishing.

However, it has been discovered that the electrical connection betweenthe conductive gas conduit 132 and the conductive passage 103 may becomesevered during use and/or during removal of the electrostatic chuck 105.Thus, the balancing circuit between the substrate spacing mask 107 andthe chucking electrodes 110 is rendered non-functional.

One embodiment for repairing a severed electrical connection in thebalancing circuit of the substrate support assembly 100 involves firsttesting the assembly to detect whether the connection has been severedand then repairing the severed connection through the use of varioustechniques and/or devices. First, the substrate support assembly istested to determine whether the electrical connection between theconductive gas conduit 132 and the conductive passage 103 has beendisrupted. In one embodiment, the resistance across the connection maybe tested via an ohmmeter. If the resistance is equal to or less than aspecified resistance, the connection is intact. If the resistance isgreater than the specified resistance, the connection must be repaired.In one embodiment, the required resistance is 200 kilo ohms (kΩ). If therequired resistance is not present, the connection is repaired.

FIG. 2 is a schematic depiction of a method of repairing the connectionbetween the conductive gas conduit 132 and the conductive passage 103according to one embodiment of the present invention. The conductivepassage 103 may be repaired by applying a coating 200 on the inside ofthe conductive passage 103. Heat may then be applied to the coating 200for a specified time period to cure the coating and re-establishelectrical continuity for the balancing circuit between the substratespacing mask 107 and the chucking electrodes 110. In one aspect, thecoating 200 bridges and electrically connects the substrate spacing mask107 to the conductive gas conduit 132.

The coating 200 may comprise a nano-particle based metal coating, suchas a silver coating. The coating 200 may be in the form of an ink or apaste that may be applied by a brush, a spray coating technique, orother suitable coating method. Suitable silver materials that may beused to coat the temperature sensor include a material sold under thetrade name TEC-PA-030 (or other materials sold under the trade nameTEC-PA-XXX, such as TEC-PA-010, TEC-PA-020, etc.), all available fromInkTec® Co., LTD of South Korea, or any other suitable conductive nanoinks that can be easily cured using IR heating, flame heating, inductionheating or furnace heating.

The coating 200 provides good adhesion with the various materials of theelectrostatic chuck 105. Thus, the coating 200 may be easily depositedon the surfaces of the first brazed joint 170, the metalized layer 175,and the surfaces of the conductive gas conduit 132. In one embodiment,the coating 200 may be a conductive nano coating/nano ink that issintered on the electrostatic chuck 105 comprising an Al/Al₂O₃/AlN, orother material. The coating 200 is used to establish proper electricalcontact with the center tap circuit. In one embodiment, the coating 200comprises a nano silver material that maintains conductivity even whenan exposed surface of the coating 200 is oxidized during curing.

The coating 200 includes particles having a size of about 10 nanometersto about 100 nanometers. The coating 200 may be deposited by numeroustechniques including spray coating, brush coating, and a printing andfiring process. The application process may comprise coating transparentsilver nano-particles in the form of an ink onto the surface. Then, theink is heated to evaporate and dry, leaving a silver organic transparentfilm to form a self assembled silver monolayer that forms the coating200. In one embodiment, the coating 200 includes an electricalresistivity at room temperature (about 27 degrees C.) that is less thanabout 0.002 micro Ohms per centimeter (μΩ cm).

The coating 200 may be cured by heating. The coating 200 may be heatedby numerous techniques including infrared (IR) light, convectionheating, microwaves, a flame-treatment, and combinations thereof. In oneembodiment, the curing comprises heating the coating 200 to atemperature of about 150 degrees Celsius (° C.) to about 200° C., andmaintaining the temperature for about 15 minutes to 30 minutes. Afterheating the coating 200, a very thin layer (e.g., having a thickness ofabout 500 nanometers (nm) to about 5 microns, such as about 20 nm toabout 100 nm) of electrically conductive material is formed between theconductive gas conduit 132 and the substrate spacing mask 107, whichprovides electrical continuity between the substrate spacing mask 107and the center tap 166 (shown in FIG. 1).

FIG. 3 is a schematic, cross-sectional view of another substrate supportassembly 300 that may benefit from the invention. The substrate supportassembly 300 includes an electrostatic chuck 105 disposed on aconductive gas conduit 132 similar to the embodiment shown in FIG. 1.The electrostatic chuck 105 includes chucking electrodes (not shown) andis electrically coupled to a power source and gas source (both notshown) similar to the configuration shown in FIG. 1. The electrostaticchuck 105 has a substrate spacing mask 107 disposed on the upper surfacethereof. A center tap structure 305 is disposed in the conductivepassage 103. The center tap structure 305 includes the center tap 166that is coupled to the conductive passage 103 by an extended member 310.The center tap structure 305 also includes a conductive member 315 thatextends away from the center of the conductive passage 103 and is incontact with the backside of the substrate 102. The center tap structure305 forms the balancing circuit as described in FIG. 1.

Similar to the substrate support assembly 100 of FIG. 1, the electricalconnection between the conductive gas conduit 132 and the conductivepassage 103 may become severed during use and/or during removal of theelectrostatic chuck 105. To repair the electrical connection, thecoating 200 as described in FIG. 2 is utilized.

Additionally, the electrostatic chuck 105 is modified to include achamfer 320 at corner regions thereof adjacent the conductive passage103. The chamfer 320 may be a beveled region that is utilized to reducestress between the conductive passage 103, and the first brazed joint170 and the metalized layer 175. The chamfer 320 may also be used toincrease surface area available for bonding with the braze materialutilized in the first brazed joint 170 and the metalized layer 175. Thechamfer 320 thus may be used to reduce stresses on the center tapstructure 305 and/or the conductive passage 103 to prevent or minimizedamage to the electrical connection between the conductive gas conduit132 and the conductive passage 103 during use and/or during removal ofthe electrostatic chuck 105.

FIG. 4 is a schematic, cross-sectional view of another substrate supportassembly 400 that may benefit from the invention. The substrate supportassembly 400 includes an electrostatic chuck 105 disposed on aconductive gas conduit 132 similar to the embodiment shown in FIG. 1.The electrostatic chuck 105 includes chucking electrodes (not shown) andis electrically coupled to a power source and gas source (both notshown) similar to the configuration shown in FIG. 1. The substratesupport assembly 400 is identical to the substrate support assembly 300of FIG. 3 with the exception of a radius 405 at corner regions of theelectrostatic chuck 105 adjacent the conductive passage 103. The radius405 may be utilized to reduce stress between the conductive passage 103,and the first brazed joint 170 and the metalized layer 175. The radius405 may also be used to increase surface area available for bonding withthe braze material utilized in the first brazed joint 170 and themetalized layer 175. The radius 405 thus may be used to reduce stresseson the center tap structure 305 and/or the conductive passage 103 toprevent or minimize damage to the electrical connection between theconductive gas conduit 132 and the conductive passage 103 during useand/or during removal of the electrostatic chuck 105.

FIG. 5 is a schematic top plan view of a substrate support assembly 500showing the center tap structure 305 described in FIGS. 3 and 4. Thecenter tap structure 305 includes the conductive member 315 having ends505 that define an open region therebetween.

Embodiments described herein provide apparatus and methods for repairinga broken electrical circuit in an electrostatic chuck. The coating andmethod as described herein provides a more economical and faster repairof the electrical connection as compared to laser and e-beam weldingtechniques, which greatly reduces cost of ownership. The coating 200also extends the lifetime of the electrostatic chuck 105 by providingimproved electrical contact that is uniform and more robust.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A substrate support assembly, comprising: an electrostatic chuckhaving an electrode embedded therein and having an aperture disposedtherethrough; a conductive liner disposed on the surface of theelectrostatic chuck within the aperture; a conductive tubing extendingfrom a lower surface of the electrostatic chuck and axially aligned withthe aperture; and a conductive coating disposed at least partiallywithin the aperture and at least partially within the conductive tubing,wherein the conductive coating provides a conductive path between theconductive liner and the conductive tubing.
 2. The substrate supportassembly of claim 1, wherein the conductive coating comprises anano-particle based metal coating.
 3. The substrate support assembly ofclaim 2, wherein the nano-particle based metal coating comprises asilver paste.
 4. The substrate support assembly of claim 2, wherein thenano-particle based metal coating comprises a silver ink.
 5. Thesubstrate support assembly of claim 2, wherein the nano-particle basedmetal coating includes a thickness of about 500 nanometers to about 5microns.
 6. The substrate support assembly of claim 1, wherein theelectrostatic chuck includes a chamfer on a portion of the apertureadjacent the conductive tubing.
 7. The substrate support assembly ofclaim 1, wherein the electrostatic chuck includes a radius on a portionof the aperture adjacent the conductive tubing.
 8. The substrate supportassembly of claim 1, wherein the conductive tubing includes a ringdisposed about an end of thereof adjacent the electrostatic chuck.
 9. Amethod for repairing a severed electrical connection within a balancingcircuit of an electrostatic chuck assembly, comprising: applying aconductive fluid across the severed electrical connection; and curingthe conductive fluid to establish a conductive path across the severedelectrical connection.
 10. The method of claim 9, wherein the conductivefluid comprises a nano-particle based metal coating.
 11. The method ofclaim 10, wherein the nano-particle based metal coating comprises asilver paste.
 12. The method of claim 10, wherein the nano-particlebased metal coating comprises a silver ink.
 13. The method of claim 10,wherein the nano-particle based metal coating includes a thickness ofabout 500 nanometers to about 5 microns.
 14. The method of claim 9,wherein the curing comprises forming a film having a thickness of about500 nanometers to about 5 microns.
 15. The method of claim 9, whereinthe curing comprises forming a film having a thickness of about 20nanometers to about 100 nanometers.
 16. A method for repairing a severedelectrical connection within a balancing circuit of an electrostaticchuck assembly, comprising: determining the resistance between asubstrate spacing mask disposed on the upper surface of an electrostaticchuck and a conductive tubing extending from the lower surface of theelectrostatic chuck and axially aligned with a metallically linedaperture extending through the electrostatic chuck; evaluating thedetermined resistance to determine whether the electrical connectionbetween the conductive conduit and the substrate mask has been severed;and repairing the severed connection by restoring a conductive pathbetween the conductive tubing and the substrate spacing mask by applyinga coating comprising a nano-particle conductive material.
 17. The methodof claim 16, wherein the nano-particle conductive material comprises afluid.
 18. The method of claim 17, wherein the nano-particle conductivematerial comprises a silver paste.
 19. The method of claim 16, whereinthe nano-particle conductive material comprises a silver ink.
 20. Themethod of claim 16, wherein the nano-particle conductive materialincludes a thickness of about 500 nanometers to about 5 microns.